The present invention relates to an electromagnetic injector for internal combustion engine fuel injection systems.
Injectors of the aforementioned type normally comprise a body with a nozzle which, for injecting fuel, is opened by a control valve which connects the control chamber of the nozzle to a drain conduit. The nozzle is normally closed by a plunger and the fuel pressure inside the control chamber, and is opened by the control valve reducing the pressure inside the chamber and raising the plunger.
The control valve on known injectors normally comprises a ball cooperating with a conical seat in a hole connecting the control chamber to the drain conduit. The ball is controlled by an element on the anchor of an electromagnet, the travel of which is such that the ball remains permanently contacting the element. Normally, the anchor also presents a rod having a conical free surface which, by means of a second ball, is arrested on an adjustable stop, also having a conical free surface, for enabling adjustable alignment of the rod in relation to the stop.
Control valves of the aforementioned type present numerous drawbacks. Foremost of these is that continual contact between the plunger and the anchor element requires highly accurate adjustment of the travel of the anchor. Moreover, the relatively heavy weight of the moving parts involved results in both sluggish closure and severe wear of the plunger due to impact.
Finally, as stoppage of the anchor by means of the second ball and the two conical seats occurs along two contact circumferences, the severe pressures involved result in the ball rutting each conical surface and forming an impression or recess. This results in impaired performance of the ball and a variation in the travel of the anchor, thus requiring frequent adjustment of the stop.